Electric field optimization on 150 kV GIS bushing using functionally gradient material

This paper deals with the electric field optimization on the bushing of 150 kV Gas Insulated Substation (GIS) using functionally gradient material (FGM). The basic bushing insulation model is made from oil impregnated paper with permittivity equals 4. The dimension of the model of the bushing before and after modification is the same. FGM is done by reducing the size of the bushing insulation basic model up to 90% and adding the material whose higher permittivity on the top of the basic material up to 100%. Mica with relative permittivity 9 is chosen as grading material. Therefore the bushing with FGM consist of oil impregnate paper with relative permittivity 4 and mica with relative permittivity 9. The mica material is placed between the conductor and oil impregnated paper. The maximum electric field intensity on 150 kV GIS bushing without modification is 80.54 kV/cm. The maximum electric field intensity is still below the electric field breakdown of oil impregnated paper (284 kV/cm). FGM modification with Mica layer reduces the maximum electric field on spacer to 66. 55 kV/cm.